[PATCH v4] iio: frequency: admv1013: fix NULL pointer dereference on str

[Antoniu Miclaus <antoniu.miclaus@analog.com>]

When device_property_read_string() fails, str is left uninitialized
but the code falls through to strcmp(str, ...), dereferencing a garbage
pointer. Replace manual read/strcmp with
device_property_match_property_string() and consolidate the SE mode
enums into a single sequential enum, mapping to hardware register
values via a switch consistent with other bitfields in the driver.

Fixes: da35a7b526d9 ("iio: frequency: admv1013: add support for ADMV1013")
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
Changes in v4:
 - consolidate SE mode enums into a single sequential enum, removing the
   separate ADMV1013_QUAD_SE_* enum and regvals lookup table
 - update commit message accordingly

 drivers/iio/frequency/admv1013.c | 65 ++++++++++++++++++--------------
 1 file changed, 37 insertions(+), 28 deletions(-)

diff --git a/drivers/iio/frequency/admv1013.c b/drivers/iio/frequency/admv1013.c
index 9202443ef445..b852378b3f68 100644
--- a/drivers/iio/frequency/admv1013.c
+++ b/drivers/iio/frequency/admv1013.c
@@ -85,9 +85,9 @@ enum {
 };
 
 enum {
-	ADMV1013_SE_MODE_POS = 6,
-	ADMV1013_SE_MODE_NEG = 9,
-	ADMV1013_SE_MODE_DIFF = 12
+	ADMV1013_SE_MODE_POS,
+	ADMV1013_SE_MODE_NEG,
+	ADMV1013_SE_MODE_DIFF,
 };
 
 struct admv1013_state {
@@ -468,10 +468,23 @@ static int admv1013_init(struct admv1013_state *st, int vcm_uv)
 	if (ret)
 		return ret;
 
-	data = FIELD_PREP(ADMV1013_QUAD_SE_MODE_MSK, st->quad_se_mode);
+	switch (st->quad_se_mode) {
+	case ADMV1013_SE_MODE_POS:
+		data = 6;
+		break;
+	case ADMV1013_SE_MODE_NEG:
+		data = 9;
+		break;
+	case ADMV1013_SE_MODE_DIFF:
+		data = 12;
+		break;
+	default:
+		return -EINVAL;
+	}
 
 	ret = __admv1013_spi_update_bits(st, ADMV1013_REG_QUAD,
-					 ADMV1013_QUAD_SE_MODE_MSK, data);
+					 ADMV1013_QUAD_SE_MODE_MSK,
+					 FIELD_PREP(ADMV1013_QUAD_SE_MODE_MSK, data));
 	if (ret)
 		return ret;
 
@@ -512,37 +525,33 @@ static void admv1013_powerdown(void *data)
 	admv1013_spi_update_bits(data, ADMV1013_REG_ENABLE, enable_reg_msk, enable_reg);
 }
 
+static const char * const admv1013_input_modes[] = {
+	[ADMV1013_IQ_MODE] = "iq",
+	[ADMV1013_IF_MODE] = "if",
+};
+
+static const char * const admv1013_quad_se_modes[] = {
+	[ADMV1013_SE_MODE_POS] = "se-pos",
+	[ADMV1013_SE_MODE_NEG] = "se-neg",
+	[ADMV1013_SE_MODE_DIFF] = "diff",
+};
+
 static int admv1013_properties_parse(struct admv1013_state *st)
 {
 	int ret;
-	const char *str;
 	struct device *dev = &st->spi->dev;
 
 	st->det_en = device_property_read_bool(dev, "adi,detector-enable");
 
-	ret = device_property_read_string(dev, "adi,input-mode", &str);
-	if (ret)
-		st->input_mode = ADMV1013_IQ_MODE;
-
-	if (!strcmp(str, "iq"))
-		st->input_mode = ADMV1013_IQ_MODE;
-	else if (!strcmp(str, "if"))
-		st->input_mode = ADMV1013_IF_MODE;
-	else
-		return -EINVAL;
+	ret = device_property_match_property_string(dev, "adi,input-mode",
+						    admv1013_input_modes,
+						    ARRAY_SIZE(admv1013_input_modes));
+	st->input_mode = ret >= 0 ? ret : ADMV1013_IQ_MODE;
 
-	ret = device_property_read_string(dev, "adi,quad-se-mode", &str);
-	if (ret)
-		st->quad_se_mode = ADMV1013_SE_MODE_DIFF;
-
-	if (!strcmp(str, "diff"))
-		st->quad_se_mode = ADMV1013_SE_MODE_DIFF;
-	else if (!strcmp(str, "se-pos"))
-		st->quad_se_mode = ADMV1013_SE_MODE_POS;
-	else if (!strcmp(str, "se-neg"))
-		st->quad_se_mode = ADMV1013_SE_MODE_NEG;
-	else
-		return -EINVAL;
+	ret = device_property_match_property_string(dev, "adi,quad-se-mode",
+						    admv1013_quad_se_modes,
+						    ARRAY_SIZE(admv1013_quad_se_modes));
+	st->quad_se_mode = ret >= 0 ? ret : ADMV1013_SE_MODE_DIFF;
 
 	ret = devm_regulator_bulk_get_enable(dev,
 					     ARRAY_SIZE(admv1013_vcc_regs),
-- 
2.43.0